World War II

Though Heisenberg submitted to the Nazi regime when necessary, his
cooperation was insufficient. He often avoided overt public acknowledgement
of the Third Reich, using the separation of science and politics
as his excuse. Moreover, he publicly opposed the efforts of Philipp
Lenard and Johannes Stark to completely discredit Einstein's work.
Lenard and Stark were Nobel Prize-winning experimental physicists
whose areas of specialty had long since become irrelevant. Indeed,
their declarations against Einstein's work as "Jewish physics"–they
believed that science was fundamentally connected to the individual
and his race and religion–were not a little influenced by their
jealousy of Einstein's renown. Heisenberg could not allow such
unreasoned criticism to pass unchallenged, and his opposition was
seen as insubordination. Lenard and Stark focused much of their
propaganda against Heisenberg, and as they were gaining administrative
power, they also succeeded in blocking his appointment to Munich
to succeed Sommerfeld.

In 1937 Heisenberg was married to Elisabeth Schumacher,
thirteen years his junior. That he should choose a young woman
was not a surprise, as he had complained recently that he needed
youth to sustain him. A book dealer, Elisabeth had been invited
to a party in Heisenberg's social circle, and they had met as he
was playing the piano. She provided him with a sense of stability
and acceptance at a time when he was feeling increasingly isolated,
especially due to the worsening conditions of his country. The
couple would have seven children and remain together for the rest
of their lives.

Meanwhile, Heisenberg's fight for the Munich appointment
continued. A petition signed by nearly all the physicists in Germany
had apparently quelled the efforts of Lenard and Stark to defeat
theory in general and Heisenberg in particular. However, Stark
made one final attempt to prevent Heisenberg's formal appointment,
publishing an article that appeared on the day of Heisenberg's
arrival in Munich, two weeks before he was to assume his chair.
The article essentially accused him of carrying the "Jewish spirit,"
which was considered worse than simply being Jewish. Heisenberg
cleared his name only after months of struggle and an appeal to
Heinrich Himmler, to whose family Heisenberg was connected through
his mother. However, the mere approval of Himmler would not be enough,
for Heisenberg also had to convince his enemies that he was loyal
to the regime. At a time when he likely faced considerable personal
danger, he saved himself only by making great compromises. As a
teacher, for example, he could not mention the names of Jewish scientists,
and as a citizen, he had to serve in the German military. If war
had broken out in 1938, he would have been sent to the front lines.
Despite his compromises, however, he still lost the Munic appointment.

Heisenberg's work, in the meantime, focused largely on
nuclear decay, along the lines of the research Enrico Fermi had
started. Heisenberg proposed the revolutionary "shower theory"
to describe cosmic radiation as explosion-like. When Heisenberg brought
this theory to the United States, his audience dwelled more on
the question of why he had chosen to remain in Germany than on his
work in shower theory. Perhaps implicitly, audiences recoiled from
accepting his work because German physics was on the decline, while
American research was on the rise.

War broke out in Europe on September 1, 1939. Heisenberg
was fully prepared to serve his country, and he expected orders
to report to the front. But the army had better use for its leading
physicists: Heisenberg and several of his experimentalist colleagues
were organized into a "uranium club" that would begin the investigation
of nuclear fission and its potential applications to the war. From
the beginning, Heisenberg did not believe that either side would
accomplish its task in time to be useful for the war.

For his side, at least, Heisenberg proved to be correct.
Perhaps in part due to a lack of resources, the Germans failed
to achieve much success in the path toward nuclear weapons. In
a famous meeting with Bohr in September 1941, Heisenberg may have
hinted otherwise, and many have speculated on his intentions in
going to Copenhagen. In all likelihood, he was not attempting some
kind of warning or truce agreement, but Bohr left with the suspicion
that Heisenberg was hinting at the extent of German progress. In
any case, the relationship between the two would never be as close
as it was before the war.